Differential gearing



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' DIFFERENTIAL GEARING.

I APPLICATION man nevi-15,1917. I I v 1A13 '55 Patented Apr. 25,1922

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J. KROHN.

APPLICATION FILED NOV- 15, l 9'l 7- I 1 113 55 7 Patented Apr. 25, 1922.Y Q I SHEETS-SHEET 4.

mill J m a a J LKROHNQ I DIFFERENTIAL BEARING.

v I APPLICATION FILED NOV-15,1917. H I 1 %18,55 v M P -25J 1s tttttsugars.

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-. J. K'ROHN.

DIFFERENTIAL GEA RING. APPLICATION FILED NOV. 15, 19H.

Patentedkpr 25, 1922.

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T H i .LKROI INQ DIFFERENTIAL (BEARING.

' I APPLICATION FILED NOV. 15, 1911. v

I Patented Apr. 25, 1922.

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siO HN KROHN, OF CHICAGO. ll lil'ill l't'iIS.

DIFFERENTIAL G31 iaiaaas.

Application filed November 15, 1917.

To all 10/1 am it may concern Be it known that I. JoHN Knot-IN, acitizen of the Fnited States of America, and a resident of Chicago.county of Cook, and State of Illinois, have invented certain new anduseful Improvements in Differential for maintaining the requiredtractive action of the driven wheel or wheels which frictionally adhereor remain in contact with the road when one or more of the group ofwheels of a vehicle has lost contactwith the road surface, or fails to'properly grip the same, due to the slippery condition of the road.

The invention consists of an adaptation of the gearing which is known aseccentric gearing, to new purposes, namely, to provide for thedifferential action required between driven shafts of power vehicles.The invention further consists in a new design of eccentric gearinginvolving a novel mode of operation.

The objects of the invention are to provide an improved differentialgearing which will meet all the before-mentioned requirements forvehicle drives. while necessitating but few and substantial elements inits structure.

An illustrative embodiment of the invention is shown in the accompanyingdrawings, in which Fig. 1 shows in transverse vertical section adifferential gearing constructed according to this invention.

Fig. 2 is a side elevation of the gearing, partly in section, along theline 22 of Fig. 1.

Fig. 3 is a horizontal sectional view the line 33 of Fig. 2.

\ Fig. 4 is a vertical sectional detail taken on the line 44 of Fig. 3.i

Fig. 5 is a detail with the casing shown in section, of a modified formof the eccenalong tric members of the differential mechanism.v

Fig. 6 is a transverse sectional view illus- Specification of LettersPatent.

Patented Apr. 25, 18 22.

Serial No. 202,126.

tirating another modification of the inven tion.

Fig. 7 is a longitudinal sectional view of the mechanism shown in Fig.6.

Fig. 8 is a longitudinal sectional view of another modified form of theinvention.

Fig. 9 is a transverse sectional view taken on the line 99 of Fig. 8.

Fig. 10 is a longitudinal sectional view taken at right-angles to thesection shown in Fig. 8.

' Fig. 11 is a transverse sectional view taken on the line 1111 of Fig.10.

Fig. 12 is a sectional detail taken on the line 12-12 of Fig. 10..

Fig. 13 is a sectional detail taken on the line 13-13. of Fig. 9.

Only a limited differential action is required between the driven wheelsof a vehicle, since the transverse distance between wheels iscomparatively slight. and therefore the radii of the circles describedby the wheels in making a turn differ only in the matter of'a few feet.The maximum increase in speed required of the outer wheel over the innerone in the ordinary turning of a vehicle is approximately a ratio of 10to 9, or less. In fact, with a vehicle having a gage of 56 inchesbetween wheels, and wheels 30 inches in diameter, the outside wheel willturn three and two-thirds times more than the inside wheel, for everycomplete turn or circular track describe-l by the vehicle. The presentinvention is designed to meet these requirements, but to make difficultneedless differential action be tween the wheels.

The present-day requirements for. vehi cle differential gearings arebelieved to be clearly set forth in an article by B. D. ()rinsby,Differential substitutes. in the bulletin of the Society of AutomobileEnineers for May, 1916. Reference is made to this article since itfairly describes the state of the art at the present time and mentions anumber of the most important devices so far provided having the same endin view as the present invention.

The drawings show a worm shaft 1 for transmitting the power from themotor to the housing 2 of the differential gearing. The shaft 1 carriesa worm 3 meshing with a worm wheel 4, fixed to the housing 2, preferablyby being clamped by-bolts 7 between the two parts 5 and 6 of thehousing. The annular web portion 8 of the wheel 4 extends within therecesses 10 and ii. the arms 15 and 16 ot the member 14 being soproportioned as to allow for the movement of the cross H with respect tothe wornrwheel radially along the recesses 10. The arms 16 ot' the crossH are each provided with an opening or slot 17. -1 pair ot externalgears 18 and 19. one ot which is located at each side of the cross H.have square lugs 20 extending into the openings l? in the cross as shownin Fig. 3. \Yith tnis construction. the cross may reciprocate along thecut-out portion 10 in the web of the worm wheel 1. thus in this movementcarrying the gears 1b and 19 with it. since the lugs ot the gears extendthrough the slot 17: while the gears may move relatively to the cross1st transversely to the direction of movement of the cross. the squarelugs 20 then moving lengthwise along the slot 17. Each of the gears 1and 19 is also provided with a single cylindrical lug or pin numbered inthe drawings 21 with respect to the gear 18, and 22 with re spect to thegear 19. These cylindrical lugs extend into drilled openings 23 at theends of a lever 24 which is journaled within the circular surt'ace onthe interior of the cross. The arms Hare internally cut away to receivethe lever 24 and permit its oscillation in the journal 25. The gears 18and 19 respectively mesh with internal gears 26 and 27 which arerotatably mounted within the sections 5 and (3 of the housing 2. Theinternal gears have webs 28 at their outer faces clear of the teeth 29of these gears and connecting their rims with their hubs 30. The hubs onthe outer side of the webs 28 provide journals for the housing byextending within th'e'portions 31 ot the sections 5 and G ot thehousing. The inner portions of the hubs 30 support eccentrics 3; uponwhich the external gears 18 and 19 are journaled. The eccentrics aretree to rotate around the hubs 3t) and within the external gears 18 andif Assuming that the dillerence in pitch diameter between the externalgears and the internal gears is one-half inch. the centers of theeccentrics are one-tourth inch to one side'ol' the center of the unit.The entire throw ol the cross 14 along the slots it) is one'halt' inch.and a motion oi one-half inch is allowed for the lugs 20 along the slots17.

Assuming that the gear 4 is stationary and the internal gears areoppositely rotated. this construction would permit the gears 18 and 19to be driven by the internal gears in a circular path without turning ontheir axes. but due to the connection provided b the.

lever it. such motion of thegears 1S and l! is necessarily in oppositedirections. and for the same reason. the t ernal gears cannot bothsimaitaneously rotate in the.

same direction with respect to the gear hous- .is retarded. or forcesare applied to the shafts in opposed directions. but in manyarrangements ot' the present differential 111801- anism. ditt'erentialaction cannot ordinarily be effected by a force applied to one shaftonly. This is due to the eccentricity of the external gears. or rather,the ratio between the internal and external gears, plus the rapidcircular motion which the external gears are compelled to execute andcommunicate to each other at the times of ditterential action. in theexample shown. there are eighteen teeth on the internal gears andsixteen teeth on the external gears. i-tccorclingly considering alonethe gearing shown in Fig. 4. it' the gear 18 is given its eccentricmotion without being permitted to turn on its axis. for every circularbodily revolution of the gear lblit will drive the internal gear thedistance of two teeth. or one-ninth of its circum'lerence. Again. byturning the gear 26. f r every two teeth it moves, it will compel thegear 18 to execute a complete circular motion without rotating on itsaxis, due to the housing being held'stationary. These are the actionswhich take place at the times of differential motion. while the housing2 is rotating. The bodily eccentric motion of the gear 1h. occurring atthe same time that the gear is rotated. drives the gear 26, due to itsconnection with the cross 14: which is rotated with the housing and wormwheel l.

For example. assuming that the entire structure is rotating and drivingthe shatts 3.3 and 36. and the shatt 36 is retarded as it would be itthe wheel which it carries were the inside wheel while turning: to theextent whiclrthe shalt IE6 is retarded. the in ternal gearZT (Fig. 1)will decrease'in speed with respect to the housing 2. thus in effectrotating baclnvardly. with respect to the housing within which it isjournaled. This action results in the external gear 1!) moving in aneccentric path with relation to the internal gear 27. and. since theexternal gear is compelled by its lug engagenn-ait with the cross torotate with the cross and the housing. the extent which it actuallydrives the ear 27 is the rliti'o rence lwtvvoon tho AFFor-k of itsrotary and eccentric motions. In order to permit this difference inspeeds of the internal and external gears, the gear 19 is compelled. inaddition to its rotation under tl action of the cross, tomove through aneccentric circle as it rolls backward on the retarded gear 27. Therolling motion of the gear 19 is permitted by the cross construction.For every circular motion of the gear 19 twcentrically with respect tothe remainder ot' the unit, the companion gear 18 is compelled toexecute a circular motion in the opposite direction. due to the leverconnection 2-1 as shown in Fig. 2. Since this eccentric motion of thegear 18 is in the same direction as the rotation of the housing and wormwheel 1. the speed of the shaft 35 will be increased over that of thehousing and worm wheel 1. Thus. if the housing is driven. say ninerevolutions per minute and the shaft 36 is retarded so as to onlyexecute eight revolutions per minute, the shaft 36 will execute tenrevolutions.

At the times of differential action, the circular motion of the gears 18and 19 is provided for by permitting the cross let to reciprocate in therecesses 10 in the flange of the gear 1. the cross 14, lever 24, andexternal gears moving as a unit in this sense, while the external gearsare permitted to recipro ate with respect to the cross in a trans versedirection as guided by the slots 17, the lever 21 oscillating. Theeccentrics 32, being loosely journaled on the hubs 30 and within theexternal gears. are compelled to accommodate themselves to the relativerotation and eccentric motion between the internal and external gears,

The ratio of the gearing or amount of eccentricity has an effect uponthe resistance which the device offers to differential action. If thereis less difference between the pitch diameters of the internal andexternal gears than that shown in the drawings. the e'ccentricity orleverage will be less and the device will offer greater resistance todifl'erential action?" Also, if there is a greater difference in pitchdiameters or the number of teeth shown in the drawings, the difierentialaction will take place with more ease.

By means of eccentric gearing. it is possible in a differentialmechanism to obtain almost any desiredresistance to differential actionor ratio, without changing the number of gears or their over alldimensions.

Therefore, as an extreme example, there mightbe one hundred teeth in theinternal gears and ninety-nine in the external gears, giving a ratio ofone hundred to one, On the other hand. there might be one-half as manyteeth in the external gears as there are in'the internal gears, with theratio of two to one. and consequently providing a considerable reductionin resistance offered to differential action. It is possible by omittingthe teeth of the gears to produce a one to one ratio.

Fig. 5 shows a modification of the eccentric elements of the inventionwherein the members 26 and 27 not shown) which are respectively securedto the driven axles are otthe same form as the members and 27 shown inFigs. 1 to 1, except that the gear teeth are omitted and an eccentriccircular recess +10 is provided for the reception of a toothlesseccentric disk 18 corresponding to the external gears 18 and 19 shown inFigs. 1 ands; A pair of these eccentric disks are connected together bymeans of the cross and lever construction previously described, andthrough the pins-2O and 21 receiving rotation from the crossconstruction in the same manner as the gears 18 and 19, and at times ofdifferential action being compelled to move in opposite eccentric pathsby means of the lever connection with the-pins 21.

The operation of this form of the invention is the same as thatpreviously described, except in the matter of ratio. Normally, theentire structure rotates as a unit, but if one of the driven axles isretarded. the corresponding eccentric 18. while still rotating withinthe recess 40 at the same angular rate at which the cross rotates, has arelative sliding motion with respect to the cross. as its square lugs 20move along the slots 17 in the cross. This relative sliding motionbetween the cross and the eccentric 18 causes a correspondingoscillation of the lever 24. and consequently, a reverse eccentricmotion of the companion eccentric.

\Vith this modified form. it is clear that the eccentric 18 can travelin its eccentric path only once for each complete relative rotation ofthe member 26. whereas in the takes this circular eccentric. motionevery time the internal gear 26, Fig. 1, rotates relatively ot' the gear18 a distance of two teeth.

' All or] 1' ficafimzs.

A modification of the invention is shown in Figs. 6 and 7. Thismodification includes the toothless eccentrics illustrated by Fig. 5;but instead of being provided with the cross and lever construction forcommunicating motion to and between the eccentrics, is protoothed formfirst described. the gear 18 pinio'ns Bland .38 are eccentricallyiournaled onstubshat'ts ("it extending tromtlne side o't' an eccentricdisk 6:2 journaled within an eccentric circular recess 63 in the membctil journaled in the part of the housing yand secured to one of thedriven axles. The pinions 5!) and (it) are likewise eccenricallyjournaled on the stub shatts extending inwardly 'lroin the side at (it;journaled in the eccentric circular recess 67 'in a circular member 68which is secured to one of the driven axles and journaled in the 'part52 oftlie housing.

In the operation of this-torm 01 the invention'. the power lirom thehousing transmitted through the member 51 to the pinions 57 to 60inclusive and through the stub shafts on which these pinions arejournaled, to the respective eccentrics 62 and (36 and from theeccentrics to the members (it and 68 respectively' secured to the drivenaxles. Normally. no relative motion occurs between the parts of thisdifferential mechanism. but it one of the driven axles is re tarded andthe other accelerated in speed when the vehicle makes a turn, theeccentrics 62 and (56 are compelled to execute circular bodily motionrelative to the housing in op posite directions. Since this motion inopposite directions. the pins (31 and (35 move in opposed circularpaths. and the pinions which are journaled thereon turn within the.

recesses 55 and 56 to acconnnodate them.- selves to the motion ot thepins. These pinions, havlng internieslnng teeth. serve to centric to theother in opposite directions.

Another modification ot'- the invention is shown in Figs. 8 to 13inclusive. This torm.

in principle. is similar to the forms previously described. in resultsobtained. and is likewise distinguishabletrom most forms of eccentricgears in that the power is transmitted to the gearing through themechanism which is arranged to'permit both rotary and relative circularmotion between f the driven eccentric members.

'journaled within disks S1 and 82 having suitably eccentric cut-outportions to receive the-eccentrics T5 and 76. The disks 81 and 82 arerespectively keyed to the 'driven axles 83 and 84. The rollers '79carried by the eccentric 75 contact with the flat surfaces 85 of theeccentric blocks 77 and 78, while the rollers 80 carried by theeccentric the block 7H being'cut away at 90 to allow clearance for therollers 80, as shown in Fig. 3; The bloc and "(t4 are also cut away attheir central ortions to. allow clearance t'or interfitting lugs 90. 91.92. and 93 formed on the inner surfaces of the eccentrics 75 and it Whendifferential action occurs with this form of the invention, assumingthat the shaft 83 is accelerated. and the shaft 84 'is retracted, therespective eccentrics 75 and 76 are compelled to make a circular motionfor every relative turn of the disks 81 and 82. clearance space 95 beingprovided between the eccentrics and the hubs 96 ot' the disks 81 and 82.Considering the non-rotary circular travel of the eccentric 75 anddisregarding its rotary motion with the entire unit. the rollers 79which it carries alternately engage the surfaces 85 and the semicircularblocks 77 and 78. Likewise, the rollers .80 ot the eccentric T6alternately engage thesurfaces 86 of the blocks TT'and 78. The result isthat these blocks oscillate in time with the circular motions of theeccentrics fronr which they receive motion. and serve to compel theeccentrics 75 and 76 to travel in opposite directions. During thisreverse motion of the eccentrics. they are guided with respect to eachother their inter-fitting lugs 90 to 93. These lugs assist in compellingthe two eccentrics to rotate togetherwith respect to rotary motionreceived from the housing. but permitting a relative sliding action inorder that the disks 31 and 82 may rotate relatively to each other.

A peculiarity ot'this invention common to all forms shown in thedrawings is that. due to the arrangement of leverage within the gearing.it is exceedin ly difticult or practically impossible to efiect.differential action merely by increasing or decreasing resistance torotation of one of the wheels. For example. one wheel might be liftedclear of the road. while the other would have good tractive contacttherewith. Irrespective of this difference in load. both wheels willrotate at the speed imparted to the ditf'erein tial from the powershat't. Thus. with this mechanism. needless differential action will nottake place when one wheel rises clear of the ground. or is in an1udhole. or slips on the pavement. To effect differential action. onewheel must ordinarily be accelerated and the other retarded with respectto the rate of rotation of the differential mechanism as a unit. Thisaction is precisely what does occur in the practical use of the1,41s,s55 I as device. When av vehicle is turning, its center travels inan are which is midway between the arcs traveled over by the inner andouter wheels. The speed of the differential mechanism as a unit isnecessarily midway between the speeds of the inner and outer wheels, theeffect being that the inner wheel is retarded, while the outer wheel isaccelerated with res met to the power shaft or line of travel of t ecenter of the vehicle. Differential action should take place when thevehicle is running in a straight course in cases where there is adifference in wheel diameters. In such cases, the larger wheel issomewhat retarded over the rate of rotation of the differential unit asa whole, while the smaller wheel is accelerated. Agaln, the power shaftrotates at a speed which is midway between the speeds of the inner anddifficult to obtain by' means of the present construction by powerapplied at one of the.

wheels only, independently of the power re- .ceived from the engineshaft.

The lever 24 which serves to transmit reverse motion between'the twoeccentric membersis not in action when both shafts are driven at thesame speed. and in the same direction, and so far as known, the forms ofthe present device which utilize said lever differ from otherdifferential mechanisms in the respect that while there is a commondriver for the two driven shafts, an inde pendent connection is providedbetween these shafts having the sole fIHICtiOIlI of transmitting reversemotion from one to the other. There is low mechanical efficiency whenthe motion is derived from one'sha-ft only, but if the motion is derivedfrom the two shafts'while they arebeing rotated in opposite directions,the mechanism is eflicient. I

The co'fi s'fructioh shown differs from most eccentric gear devices inthat the mechanism which permits differential action between the twodriven members is in itself the driver. Heret'ofore, eccentric gearshave been used mainly as power transmitting and speed changing orreversingmeans. The advantages in general of such gearing over mostmechanical constructions for such purposes are the great amount ofleverage possible within a Very limited space,'its high efficiency, dueto the practical absence of friction, since there is little, if any,rubbing contact between the faces of the intermeshing gear teeth, andits great strength and durability, due to the surface area of thecontacting portions of the teeth. All these advantages are inherent inthe present adaptation of eccentric gearing, but the arrange ment issuch that easy differential action is only possible under conditionswhere it is required, and is extremely difficult to obtain when theseconditions are not-fully met.

Of course, resistance to differential action in the present constructionisdue mainly tothe eccentricity of the eccentric members of thedifferential. This eccentricity may be varied so as to make differentialaction com-.

it would be driven merely at the same speed as'the wheel which doescarry, the load. Accordingly, one of the axles might be broken withoutpreventing continued use of the vehicle, since the same could be drivenby one wheel. This is believed to be particularly advantageous inconnection with army trucks, et' cetera.'which must at times be drivenover rough roads.

It will be understood that numerous details of the construction. shownmay be altered or omitted without departing from the spirit of thisinvention as defined by the following claims.

I claim: I

1. In a device of the class described, differential mechanism, means fordriving said differential mechanism, a. pair of driven shafts, andtoothed eccentric gearingwithin' ing two pairs of eccentrically arrangedgears for respectiely'driving said shafts.

3. In adevice of the class described,differential mechanism, means fordriving said differential mechanism, a pair of driven shafts, saiddifferential mechanism compris ing two pairs of eccentrically arrangedgears for respectively driving said shafts, and a connection fortransmitting motion between said pairs of gears.

4. A differential gearing, comprising a driven member, and a pluralityof pairs of eccentrically arranged gears, said driven member havingconnections to each of said pairs of gears, said member being arrangedto transmit rotational motion to the pairs of gears while permitting themembers of each pair to have a relative eccentriemotion.

5. A differential. gearing. comprising a driven member. a plurality ofpairs of eccentric-ally arranged gears. said driven memher havingconnections to each of said pairs of gears. said member being arrangedto transmit rotational motion to the pairs of gears \vhile permittingthe members of each pair to have a relative eccentric motion, and meansfor transmitting eccentric motion from one pair of gears to the other inan opposite direction.

6. A differential mechanism, comprising a driven member, and a pluralityof pairs of eccentric members, each pair having one eccentric memberWithin the other. said driven member having a driving connection to oneeccentric member of each pair.

7. A differential mechanism. comprising a driven member. a plurality ofpairs of eccentric members, each pair having one eccentric member Withinthe other. said driven member having adriving connection. to oneeccentric member of each pair, and means for t'a-nsmi'tting motion fromone pair of eccentric members to another pair of eccentric members inany opposite direction.

8. A differential mechanism, comprising a pair of driven eccentrics,means for rotating said eccentrics on their axes in the same: direction,said means being arranged to permitsaid eccentrics to move in oppositecircul-ar paths, and a pair of concentric driven members havingeccentric journals for supporting said eccentrics.

9. An eccentric gearing. comprising a pair of driven eccentric gears.said gears being arranged to revolve around a common axis and toindependently rotate on their own axes, and means for transmittingmotion'in opposite directions from one of said gears to the other. saidmeans being also arranged to drive both of said gears in the samedirection. 7

10. An eccentric differential gearing, comprising two driven members,eccentric gearing associated with each member, and means connecting saidgearing arranged to transmit motion from one driven member to the otherat a substantially one to oneratio but in. opposite direction.

11. Differential mechanism, comprising a pair of driven concentricmembers, a pair of gyratory members for driving said driven members."means for imparting motion to said gyratory members in a common direc-vtion, and a'lever connecting said gyratory members whereby independentmotion may be reversely communicated from one to the other.

12. A differential mechanism, comprising a pair of driven shafts, a pairof eccentrically supported members each of which is arranged in drivingrelation with one of said shafts, means for driving both of said membersin the same direction, and a connection between said members forcommunicating an independent motion from one to the other in.a reversedirection only. I

13. A differential mechanism, comprising two driven members, a driver,separate gears connected between said driver and each of said drivenmembers, means movably mounted on each of'said gears for controlling itsaction, and a connection between said movably mounted means to preventrelative motion of said gears except in opposite directions.

14. In a device of the class described, differential mechanism, meansfor driving said differential mechanism, a pair of. driven shafts, saiddifferential mechanism comprising two pairs of eccentrically arrangedgears for respectively driving the said shafts, and a connection betweenone gear of each pair adapted to secure said one gears against rotationon their own axes, but. permit said one gears t.o revolve in oppositedirections about the axis of said driving shafts.

S ggned at Chicago this 12th day of -Nov., 191

JOHN KR-OHN.

